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Biomedical subjects

J Palau

Publications and source records attributed to J Palau.

At least 55 records · Page 3Linked to original sources
PubMed1988

Signal recognition-like particles are present in maize.

We show that maize storage protein translocation across microsomal membranes is mediated by signal recognition particles (SRPs) similar to those described in animal systems (Dobberstein, B. (1978) Hoppe-Seyler's Z. Physiol. Chem. 252, 955-962; Walter, P., and Blobel, G. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 7112-7116). We have prepared a high salt extract from endosperm cell homogenates, from which a ribosome-free fraction was obtained. This fraction is enriched in an SRP-like factor which apparently corresponds to a ribonucleoprotein particle that sediments at about 12 S. The RNA moiety of this 12 S particle is complex, showing a three-band electrophoretic pattern and sedimenting at about 8 S. The fraction restores translocation competence of salt-washed maize microsomes as tested by using a pre-zein message. In contrast to canine SRPs, the maize SRP-like component does not cause a translation arrest of maize storage proteins (zein) in a wheat germ cell-free system.

Animals↗
PubMed1988

The b-32 protein from maize endosperm, an albumin regulated by the O2 locus: nucleic acid (cDNA) and amino acid sequences.

The cDNA coding for the b-32 protein, an albumin expressed in maize endosperm cells under the control of the O2 and O6 loci, has been cloned and the complete amino acid sequence of the protein derived. A lambda gt11 cDNA library from mRNA of immature maize endosperm was screened for the expression of the b-32 protein using antibodies against the purified protein. One of the positive clones obtained was used to isolate a full-length cDNA clone. By Northern analysis, the size of the b-32 mRNA was estimated to be 1.2 kb. Hybrid-selected translation assays show that the message codes for a protein with an apparent molecular weight of 30-35 kDa. The nucleotide sequence shows that several internal repeats are present. The protein has a length of 303 amino acid residues (mol. wt. 32430 dalton) and its sequence shows the following features: no signal peptide is observable; it contains seven tryptophan residues, an amino acid absent in maize storage proteins; polar and hydrophobic residues are spread along the sequence; several pairs of basic residues are present in the N-terminal region; the secondary structure allows the prediction of two structural domains for the b-32 protein that would fold up giving rise to a globular shape. The cloning of this gene may help in understanding the role of the O2 and O6 loci in regulating the deposition of zein, the major storage protein of maize endosperm.

Amino Acid Sequence↗
PubMed1987

SS-B (La) nuclear antigen. Organization in structural domains of the protein moiety.

Stable degradation products, obtained by digestion with endogenous and V8 proteases of calf thymus SS-B (La) antigenic protein, have been studied. The most characteristic fragments have molecular masses of 47, 30, 23 and 17 kDa. The 47-kDa and 30-kDa fragments are complex and are constituted of a number of species of different isoelectric points, as has been described for the SS-B protein molecule from other sources. Degradation products from the entire SS-B nuclear antigen still contain the 30-kDa SS-B fragment, suggesting that the 30-kDa region of the SS-B protein molecule is firmly attached to the RNA moiety. A model is presented that implies the presence of two hinge regions sensitive to proteases and three structural domains that correspond to segments of 30 kDa, 17 kDa and 5-6 kDa.

Amino Acid Sequence↗
PubMed1987

Studies on the stability of the higher-order structure of rat liver chromatin containing high-mobility-group proteins.

The stability of the higher-order structure of chromatin containing high-mobility-group (HMG) proteins has been studied in rat liver nuclei by mild micrococcal nuclease digestion at low temperature and fractionation by sucrose gradient centrifugation. Nuclei preparation and digestion, chromatin solubilization and analysis have been carried out in two ionic conditions, 140 mM and 40 mM monovalent cation concentration, avoiding drastic changes in ionic conditions and temperature during preparation and analysis. During the time course of digestion at 140 mM ionic strength a material stable at 80 S appears, whose DNA is cleaved at values around 12 nucleosomes. The distribution of HMG proteins in different chromatin fractions was analyzed by immunodot using antibodies elicited against proteins HMG-1, HMG-2, and HMG-14 and 17. It appears that these proteins have a distribution distinctly different from the bulk of chromatin. They are never found in the chromatin fragments that keep their internucleosomal interactions, indicating that these proteins tend to accumulate in points where the chromatin has a less stable structure.

Animals↗
PubMed1986

A multiple sample immunoblotting system (MSIS) for the intrinsic detection of antinuclear autoantibodies.

A multiple sample immunoblotting system (MSIS) is described. The MSIS permits the detection and classification of antinuclear antibodies (ANA) according to the pattern of antigenic polypeptides recognized in four different extracts: calf thymus whole tissue, nuclear extract, and two ammonium sulphate fractions of the nuclear extract. The procedure permits the classification of anti-RNP, anti-SS/B and anti-Sm, and the detection of new ANAs in sera from SLE patients. The reaction patterns presented are specific and unambiguous, and make the use of validated control sera unnecessary.

Antibodies, Antinuclear↗
PubMed1985

Structural studies on Allium cepa L. chromatin: enhanced stability of internucleosome interactions in plant chromatin.

The pattern of micrococcal nuclease digestion of chromatin from different organs of Allium cepa has been studied. The DNA from small oligonucleosomes appears to be highly degraded and heterogeneous. In solutions of intermediate ionic strength (0.15 M NaCl) histones H2A and H2B form dimers, however at high salt concentrations (2 M NaCl) they tend to form complexes of higher order, such as tetramers. It is proposed that a correlation exists between the ability of these proteins to form tetramers and the particular stability of internucleosome interactions.

Centrifugation, Density Gradient↗
PubMed1985

Nucleic acid (cDNA) and amino acid sequences of the maize endosperm protein glutelin-2.

The cDNA coding for a glutelin-2 protein from maize endosperm has been cloned and the complete amino acid sequence of the protein derived for the first time. An immature maize endosperm cDNA bank was screened for the expression of a beta-lactamase:glutelin-2 (G2) fusion polypeptide by using antibodies against the purified 28 kd G2 protein. A clone corresponding to the 28 kd G2 protein was sequenced and the primary structure of this protein was derived. Five regions can be defined in the protein sequence: an 11 residue N-terminal part, a repeated region formed by eight units of the sequence Pro-Pro-Pro-Val-His-Leu, an alternating Pro-X stretch 21 residues long, a Cys rich domain and a C-terminal part rich in Gln. The protein sequence is preceded by 19 residues which have the characteristics of the signal peptide found in secreted proteins. Unlike zeins, the main maize storage proteins, 28 kd glutelin-2 has several homologous sequences in common with other cereal storage proteins.

Amino Acid Sequence↗
PubMed1984

Interaction between domains in chromosomal protein HMG-1.

Peptides corresponding to the N-terminal, central and central plus C-terminal domains of high mobility group protein HMG-1 from calf thymus have been isolated after digestion in solution with protease V8 under structuring conditions (0.35 M NaCl, pH 7.1). The effect of the interaction of these peptides with DNA on the topological properties of the nucleic acid has been studied and compared with the change in superhelicity produced by the whole protein. It appears that the region responsible for this effect is the central domain of HMG-1. The isolated N-terminal and central domains of this protein maintain their secondary and tertiary structure as observed by spectroscopic techniques. However, when the central domain is covalently linked only to the acidic C-terminal part of the molecule, its secondary and tertiary structures are lost as well as its property to alter DNA superhelicity. The results are discussed in relation to the interactions occurring between the different domains and the possible functional interactions of this protein.

Amino Acids↗
PubMed1984

Characterization of antigenic polypeptides of the RNP, Sm and SS-B nuclear antigens from calf thymus.

Antinuclear autoantibodies are a hallmark of autoimmune diseases. The RNP, Sm and SS-B nuclear antigens from calf thymus in whole tissue, nuclear extracts and fractions have been studied by using different techniques including immunodiffusion, counterimmunoelectrophoresis and protein blotting. Such studies were done in order to obtain a precise characterization of the polypeptide components of those antigens. From our results it can be established that: one 69.8 Kd polypeptide (for whole tissue and nuclei) and a number of well-defined 32-38-Kd polypeptides (for nuclear extracts and ammonium sulfate fractions) show an antigenic character against anti-RNP sera; anti-Sm sera from different patients show in all cases a variable component of antigenic polypeptides, including one 28.8, 29.7 Kd doublet and two singlets of 14.8 and 11.0 Kd; and a 52.0-Kd SS-B antigenic polypeptide is found for whole tissue, which is gradually degraded in nuclei and nuclear extracts to a more stable 47.1-Kd polypeptide.

Animals↗
PubMed1984

Association-dissociation of histone oligomers. A spin label study.

The spin label method has been used to obtain information about conformational changes of histone oligomers taking advantage of the fact that at a low ionic strength and in the presence of other histones about 45% of cysteine residues of histone H3 react with the 3-maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl spin label. For the labeled complexes H3-H4 and H nu the degree of immobilization of the spin label is a function of the ionic strength. This variation is identical for both complexes within a long range of ionic strengths, including the interval of 0.8-2 M NaCl, under which conditions interactions are known to exist between the tetramer (H3)2 (H4)2 and the dimer (H2A) (H2B). This finding suggests a negligible influence of the dimer for modifying the cysteine residue environment of histone H3 on octamer formation. GuHCl treatment at high ionic strength of the labeled complexes gives rise to a non-lineal increase in the degree of mobility of the spin label. This increase, at low GuHCl concentration (0-0.5 M GuHCl), is interpreted as showing a lowering in rigidity for the Cys residue environment, without affecting the general stability of the tetramer (H3)2 (H4)2. At higher GuHCl concentration (2-3 M GuHCl) the increase in the spin label mobility is related to a dissociation of the complexes in single histones. Our results are consistent with the view that the overall structure of the tetramer, as well as its conformational changes during complex structuration or denaturation, are not strongly affected by the presence of the dimer (H2A) (H2B).

Cysteine↗
PubMed1983

DNA and histone H1 interact with different domains of HMG 1 and 2 proteins.

High mobility group (HMG) proteins 1 and 2 from calf thymus have been digested under structuring conditions (0.35 M NaCl, pH 7.1) with two proteases of different specificities, trypsin and V8. The two proteases give a different but restricted pattern of peptides in a time course digestion study. However, when the interactions of the peptides with DNA are studied by blotting, a closely related peptide from HMG-1 and -2 does not show any apparent binding. This peptide, from the V8 protease digestion, has been isolated by DNA-cellulose chromatography and has the amino acid composition predicted for a fragment containing the two C-terminal domains of the protein, i.e., approximately residues 74-243 for HMG-1. The same peptide shows the only interaction detectable with labelled histone H1. A separate function for the different domains of HMG proteins 1 and 2 is proposed.

Amino Acids↗
PubMed1983

Antigenic variability among very-lysine-rich histones from calf thymus and from sperm of different echinoderms.

1. Very-lysine-rich histone of a mammal (calf thymus), two sea urchins (Arbacia lixula and Paracentrotus lividus) and a sea cucumber (Holothuria tubulosa) were compared by using immunological techniques. 2. The degree of antigenic variability among all these histones was measured by quantitative microcomplement fixation. An evoluntionary diagram for this group of histones has been established. 3. The histone from sea cucumber is placed in an intermediate situation between those for calf thymus and sea urchins, and the immunological distance between the histones of the two urchins is very short.

Amino Acids↗
PubMed1982

Amino acid distribution in protein secondary structures.

The compositional distribution of the twenty amino acids was examined for particular positions within secondary structures (alpha-helices, beta-strands, and turns) taken from a 44-protein sample. Correlation coefficients calculated between positional composition of the amino acids and various of their physico-chemical characteristics indicated considerable asymmetry in the properties of the residues comprising regions within and adjacent to secondary structures, modes of helix formation, physical parameters most sensitive to the buriedness of residues in beta-strands, and possible improvements in the accuracy of secondary structure prediction methodologies.

Amino Acids↗
PubMed1982

Protein secondary structure. Studies on the limits of prediction accuracy.

A secondary structure prediction technique is proposed which includes nucleation site determination through multiplication of conformational preference parameters as well as weighting factors to represent structurally stabilizing short range interactions. The prediction accuracy of the method is calculated using data bases categorized according to the four protein structural classes and with differing assignments of secondary structural regions. The results indicate that nearest neighbor prediction techniques (a) are insensitive to various assignment criteria for the secondary structural spans, (b) have nearly achieved their upper limit of prediction accuracy, and (c) can be somewhat improved through the use of stereochemical weighting factors and conformational parameters derived from the four structural groups.

Chemical Phenomena↗
PubMed1980

The structure of sea-urchin-sperm histone phi 1 (H1) in chromatin and in free solution. Trypsin digestion and spectroscopic studies.

The lysine-rich H1-type histone phi 1 from the sperm of the sea urchin Arbacia lixula has been subjected to tryptic digestion in free solution at high ionic strength. Tw trypsin-resistant peptides G phi 1 and LG phi 1 have been isolated, comprising 81 and 95 amino acids respectively, i.e. about a third of the intact histone. Circular dichroism and 270-MHz proton NMR have been used to demonstrate that the smaller peptide G phi 1 contains all the secondary and tertiary structure of intact histone phi 1. It is concluded that the resistant peptides represent a compact folded portion of the histone phi 1 chain, whilst the remaining two-thirds is disordered in free solution. Trypsin digestion of Arbacia lixula nuclei, under conditions where histone phi 1 remains tightly bound to the chromatin, leads to the same resistant peptide G phi 1. From this it is concluded that in chromatin the chain region corresponding to G phi 1 is likewise folded and inaccessible to trypsin, whilst the remaining exposed residues are located periferally and probably in an extended conformation. The rather unusual H1-type histone phi 1 from sea urchin sperm thus has a three-domain structure like calf thymus H1 and chicken erythrocyte H5. The present data emphasise the fact that this three-domain structure exists in chromatin and is not merely a free-solution artefact.

Animals↗
PubMed1978

On the interaction of histone Hl and Hl peptides with DNA. Sedimentation, thermal denaturation and solubility studies.

The interactions in buffered 0.14 M NaCl (pH 7.0) of DNA, native or sonicated, with histone Hl and with its fragments N-Hl (residues 1-72) and C-Hl (residues 73-COOH), have been studied by using the techniques of sedimentation, thermal denaturation and solubility. Histone Hl shows a preferential affinity for high molecular weight DNA in comparison with sonicated DNA. The binding of histone Hl to sonicated DNA in 0.14 M NaCl is reversible and the reversibility decreases with time. These findings are consistent with the view that Hl is cooperatively distributed along DNA molecules and that this distribution is energetically more favoured for long DNA than for sonicated DNA. It has been found that under conditions of moderate salt concentration, the C-terminal region is the main one responsible for the interaction of Hl with DNA, and also for a cooperative distribution of the histone along the DNA molecules. Addition of urea to the solution produces a decrease of solubility of Hl-DNA complexes. This effect reflects an additional condensation of the complex, which is probably related to the unfolding of the globular part of the histone. It is suggested that this globular region does not play a substantial role in the condensation of Hl-DNA complexes. A model which takes into account the presence of free lysyl and phosphate groups within the complex is discussed.

Animals↗